Preparation of detergent compositions



3,031,498 PREPARATION OF DETERGENT COMPOSHTIGNS Peter John Pengilly, Stockslield, Northnmherland, England, assignor to The Procter Gamble Company, Cincinnati, Ohio, a corporation of Ohio No Drawing. Filed Feb. 4, 1958, Ser. No. 713,093 Claims. (Cl. 26tl-505) This invention relates to improvements in and relating to the preparation of detergent compositions, especially to sulphonation processes, and is more particularly concerned with an improved process for reducing the inorganic sulphate content of a sulphonated product such as is suitable for use in the manufacture of detergent compositions.

In the manufacture of organic anionic sulphonate detergents it is customary to treat an organic material such as alkyl aryl hydrocarbon, the molecule of which contains an alkyl group of 8 to 20 carbon atoms, with an excess of a sulphonating agent, such as sulphuric acid, oleum or sulphur trioxide.

In such sulphonation processes there is obtained as reaction product a mixture which contains the desired sulphonic acid in admixture with free sulphuric acid, and there may also be present some free sulphur trioxide if oleum or sulphur trioxide has been used as sulphonating agent. In the manufacture of powdered detergents where a substantial proportion of inorganic salt may be tolerated, or may even be desirable, in the finished product, it is customary to neutralise the sulphonation product with a suitable alkali and work up the neutralised product into the desired physical form, possibly after the addition of other materials such as alkali builders. It is, however, desirable that certain types of detergent compositions, for example liquid detergent compositions or shampoos, should have a low content of inorganic sulphate, such as results from neutralisation of the free sulphuric acid in the sulphonation product. 4

It has been proposed to remove part of the free sulphuric acid in the sulphonation product by allowing the reaction product to settle, if necessary after the addition of some water, and running ofi the aqueous sulphuric acid layer which separates. This process does not, however, reduce the inorganic sulphate content of the finished product to such a low level as is desired for the liquid detergent and shampoo products referred to above.

It has been further proposed to purify the sulphonation product by solvent extraction of the unneutralised acid product, or of the neutralised product either before or after drying.

It has now been discovered that free sulphuric acid and inorganic sulphate can be substantially eliminated in an effective way, if, after first removing free sulphuric acid from the sulphonation product in a pre-treatment by a known method, e.g. by settling and running off or by centrifuging, the pretreated product is mixed with an aliphatic C1 to C4 alcohol and/or a C3 to C4 ketone, and water and with an agent in an amount calculated as sufficient to react with the free sulphuric acid present in the reaction mixture so as to form a crystallisable sulphate but not substantially more than sufiicient to neutralise the free sulphuric acid completely, and the inorganic sulphate so obtained, which is deposited as crystals or as sludge, is removed.

Accordingly, the invention provides a process for the preparation of a detergent composition of low inorganic salt content, in which the acid reaction mixture obtained by sulphonation of an organic material having an alkyl group of from 8 to 20 carbon atoms in the molecule,

after preliminary removal of free sulphuric acid by a known process,e.g. settling and running off, or centrifuging, is mixed with at least 20% of its ownweight of a tent "ice 3,h3l,498 Patented Apr. 24, 1962 C1 to C4 aliphatic alcohol and/or a C3 to C4 ketone, including a mixture of two or more of such alcohols, an amount of water which is not greater than the weight of alcohol and/or ketone used, and an agent in an amount calculated as sufficient to react with the free sulphuric acid present in the reaction mixture so as to form a crystallisable sulphate but not substantially more than sufficient to neutralise the free sulphuric acid completely, to precipitate inorganic sulphate, the precipitated material so obtained in the treated reaction mixture is separated, and the resulting purified sulphonic acid neutralised and worked up to the required finished product.

The process of the invention is suitable for the treatment of the products of true sulphonation reactions, for example the sulphonation of alkyl aromatic compounds such as dodecylbenzene. It is not suitable for use with the products of sulphation reactions such as for example the sulphation of fatty alcohols, as such sulphation products are liable to undergo hydrolysis due to the addition of water during the preliminary layering or other process by which free sulphuric acid is removed.

Ethanol has given very good results in the process of the invention but other C1 to C4 aliphatic alcohols and C3 to C4 ketones may be used, including other monohydric alcohols, methanol, propanol, iso-propanol, butanol and iso-butanol, dihydric alcohols such as propylene glycol, and C3 to C4 ketones such as acetone. Mixtures of such alcohols and/or ketones may be used, if desired. For reasons of economy it is preferred to keep the amount of alcohol and/ or ketone as low as possible, but for satisfactory operation the amount should be at least 20% by weight of the acid reaction mixture which is treated.

The weight of water added may be varied provided that it is not greater than the weight of alcohol and/ or ketone used. Increasing the amount of water leads to less complete precipitation of the inorganic sulphate, while decreasing the amount of water leads to some precipitation of the sulphonic acid with inorganic sulphate in the sludge.

As agent for neutralising the free sulphuric acid, it is preferred to use caustic soda but other materials such as soda ash, sodium bicarbonate, potassium carbonate, potassium bicarbonate, caustic potash, and mixtures thereof, and ammonia, may also be used. It is an advantage of the process of the invention where it is ultimately desired to neutralise the sulphonic acid with some relatively costly base, such as caustic potash or triethanolamine, as is frequently required for liquid detergent compositions, that it is not necessary to use the same base to neutralise the unwanted free sulphuric acid in the mixture.

As has already been indicated, the quantity of the agent used is sufficient to form a crystallisable sulphate. Such crystallisable sulphates include the neutral sulphate, e.g. Na SO and also acid sulphates such as NaHSO and double or mixed sulphates formed from the nuetral and/or acid sulphates. Preferably the amount of agent used is such as to precipitate the acid sulphate, e.g. NaHSO or KHSO The water, alcohol and/or ketone, and neutralising agent may be added to the pretreated sulphonation product in any desired order, although it is preferred to add the alcohol and/ or ketone simultaneously with or before the neutralising agent. For example, the neutralising agent may be dissolved in a mixture of the water and alcohol and/ or ketone and the resulting mixture may then be stirred into the pretreated sulphonation product. The sludge which is precipitated may be removed by any desired method, such as decanting, filtering or centrifuging. It is advantageous to wash the sludge removed from one batch with the fresh alcohol and/or ketone which assures the sludge can be extracted and returned to the process.

The temperature at which the process is carried out should not be so low that difficulties are experienced as a result of high viscosity, nor so high that there is appreciable darkening of the colour of the sulphonic acid mixture. A suitable temperature range has been found to be 50 F. to 130 F.

The purified sulphonic acid obtained by the process of the invention may be neutralised with any desired base and worked up to the required finished product.

The alcohol and/ or ketone may be recovered for re-use by distillation from the neutralised purified sulphonic acid or, if the finished product is to be a liquid composition in which alcohol and/or ketone is a desirable solvent ingredient, it may be left in the product.

When working at the temperatures mentioned above, during the whole of the process up to the stage of neutralising the purified sulphonic acid, the material is liquid which is convenient to handle, even though the sulphonic acid content may be of the order of 60%.

The following examples are given for the purpose of illustrating the invention; all parts, ratios and percentages are by weight.

Example I The acid reaction product from the sulphonation of dodecylbenzene with 25% oleum using a ratio of oleum to alkylbenzene of 1.06:1 was mixed with water until the aqueous layer had a concentration of 78% H 80 The mixture was allowed to settle and the lower layer, consisting of aqueous sulphuric acid, was run oft. The remaining upper layer contained alkylbenzene sulphonic acid and sulphuric acid in the ratio 10:1.

To 200 parts of this upper layer material (consisting of 182 parts alkylbenzene sulphonic acid and 18 parts sulphuric acid) were added 76 parts of industrial methylated spirits. A solution of 14.7 parts of sodium hydroxide in 20 parts water was then stirred into the material, the mixture being stirred and cooled to prevent the temperature. rising above 130 F. After addition of alkali the mixture Was cooled to 120 F. and centrifuged for 15 mins. at 2,500 r.p.m. 31.5 parts of sludge were separated from 279.2 parts of liquid consisting of:

Sludge Liquid Parts sodium sulphate 19. 5 6. 5 Parts allrylbenzene sulphonic acid. 6. 176 Parts ethanolm; 4. 67; 5 Parts water 1. 6 29. 2

The sludge was mixed with a further 53 parts of industrial methylated spirit and centrifuged again. 32.0 parts of sludge were separated from 52.5 parts of liquid consisting of:

Sludge Li quid Parts sodium sulphate 19. 5 Parts allrylbenzene sulphonic acid. l. 6 4. 4 Parts ethanol l0. 0 44. 5 Parts water 0. 9 3. 6

The liquid was used as solvent for a subsequent batch.

Example 2 of acetone. A solution of 18 parts of sodium hydroxide in 36 parts of water was then stirred into the material, the mixture being cooled to prevent the temperature rising above 130 F. After addition of alkali the mixture Was cooled to 120 F. and centrifuged for 10 minutes at 2500 r.p.m. 66 parts of sludge were removed and the remaining liquid had a ratio of alkylbenz/ene sulphonic acid to sulphuric acid of 19.5 :1.

Example 3 Example 4 A mixture of 9.07 parts of dodecylbenzene and 0.63 part of toluene was sulphonated with 10.75 parts of 25 oleum to produce 20.45 parts of reaction mixture. The reaction mixture was mixed with 1.90 parts of water and allowed to settle into two layers, the lower layer consisting of 7.87 parts of 78% sulphuric acid, being run oft, leaving 14.48 parts of a mixture'containing sulphonic acids and free sulphuric acid, the mixture containing 1.16 parts of free H 50 To this separated acid mixture was added a mixture of 0.79 part of caustic potash, 0.7 part of water, and 7.5 parts of industrial methylated spirit. The resultant precipitate was removed by filtration leaving 21.42 parts of clear liquid which contained no measurable quantity of free sulphuric acid or sulphate.

The precipitate consisted of 1.62 KHSO with only a trace of organic What is claimed is:

1. In a process for the preparation of a detergent compostion of low inorganic salt content, in which the reaction mixture is obtained by sulphonation of alkylbenzene having an alkyl group of 8 to 20 carbon atoms in the molecule to form a sulphonic acid phase and an aqueous sulphuric acid phase, the steps of (1) separating the aqueous sulphuric acid phase and removing it from the reaction mixture (2) mixing the reaction mixture with at least 20% of its own weight of a lower alkyl aliphatic solvent selected from the group consisting of C to C alcohols and C to C ketones, an agent selected from the group consisting of caustic soda, soda ash, sodium bicarbonate, potassium carbonate, potassium bicarbonate, caustic potash, and mixtures thereof, and ammonia in an amount calculated as being at least sufficient to react with the free sulphuric acid present in the reaction mixture so as to form a crystallisable sulphate which precipitates, and at most substantially the amount required to neutralise and free sulphuric acid completely, and an amount of water such that the total water in the is at most substantially the weight of said lower aliphatic solvent used, is not greater than that required to promote substantially complete precipitation of the crystallisable sulphate and is not less than that required to avoid precipitation of said sulphonic acid with the precipitated sulphate (3) separating the precipitated material so obtained (4) neutralising said sulphonic acid and working up the required product.

2. A process according to claim 1, wherein the said agent is added to the reaction mixture in aqueous solution and is selected from the group consisting of the hydroxides, carbonates and bicarbonates of sodium and potassium, and mixtures thereof.

3. A process according to claim 1, wherein the said agent is added to the reaction mixturein aqueous solution and is sodium hydroxide.

parts of crystals of material.

4. A process according to claim 1, wherein the amount of said agent is such as to form a crystallisable acid sulphate.

5. A process according to claim 1, wherein the said agent is added to the reaction mixture in aqueous solution and is sodium hydroxide and the amount is such as to form sodium hydrogen sulphate.

6. A process according to claim 1, wherein the said agent is added to the reaction mixture in aqueous solution and is potassium hydroxide and the amount is such as to form potassium hydrogen sulphate.

7. A process according to claim 1, wherein the said lower aliphatic compound is ethanol.

8. A process according to claim 1, wherein the steps of mixing and separating are carried out at from 50 F.

to 130 F.

6 current process is carried out by washing the said precipitated material with fresh said lower aliphatic compound and then using said lower aliphatic compound obtained from said washing for mixing with a further quantity of said reaction mixture.

10. A process according to claim 1, wherein the sepa- Y rating step is carried out by centrifugal separation.

9. A process according toclairn 1, wherein a counter- References Cited in the file of this patent UNITED STATES PATENTS UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent. No. 3,031,498 April 24 1962 Peter John Pengilly It is hereby certified that error appears in the above numbered patsaid Letters Patent should reades ent requiring correction and that the corrected below.

Column 4, line 59, for "and" read the Signed and sealed this 21st day of August 1962,

(SEAL) Attest:

ESTON G. JOHNSON DAVID LADD Commissioner of Patents Attesting Officer 

1. IN A PROCESS FOR THE PREPARATION OF A DETERGENT COMPOSITION OF LOW INORGANIC SALT CONTENT, IN WHICH THE REACTION MIXTURE IS OBTAINED BY SULPHONATION OF ALKYLBENZENE HAVING AN ALKYL GROUP OF 8 TO 20 CARBON ATOMS IN THE MOLECULE TO FORM A SULPHONIC ACID PHASE AND AN AQUEOUS SULPHURIC ACID PHASE, THE STEPS OF (1) SEPARATING THE AQUEOUS SULPHURIC ACID PHASE AND REMOVING IT FROM THE REACTION MIXTURE (2) MIXING THE REACTION MIXTURE WITH AT LEAST 20% OF ITS OWN WEIGHT OF A LOWER ALKYL ALIPHATIC SOLVENT SELECTED FROM THE GROUP CONSISTING OF C1 TO C4 ALCOHOLS AND C3 TO C4 KETONES, AN AGENT SELECTED FROM THE GROUP CONSISTING OF CAUSTIC SODA, SODA ASH, SODIUM BICARBONATE, POTASSIUM CARBONATE, POTASSIUM BICARBONATE, CAUSTIC POTASH, AND MIXTURES THEREOF, AND AMMONIA IN AN AMOUNT CALCULATED AS BEING AT LEAST SUFFICIENT TO REACT WITH THE FREE SULPHURIC ACID PRESENT IN THE REACTION MIXTURE SO AS TO FORM A CRYSTALLISABLE SULPHATE WHICH PRECIPITATES, AND AT MOST SUBSTANTIALLY THE AMOUNT REQUIRED TO NEUTRALISE AND FREE SULPHURIC ACID COMPLETELY, AND AN AMOUNT OF WATER SUCH THAT THE TOTAL WATER IN THE MIXTURE IS AT MOST SUBSTANTIALLY THE WEIGHT OF SAID LOWER ALIPHATIC SOLVENT USED, IS NOT GREATER THAN THAT REQUIRED TO PROMOTE SUBSTANTIALLY COMPLETE PRECIPITATION OF THE CRYSTALLISABLE SULPHATE AND IS NOT LESS THAN THAT REQUIRED TO AVOID PRECIPITATION OF SAID SULPHONIC ACID WITH THE PRECIPITATED SULPHATE (3) SEPARATING THE PRECIPITATED MATERIAL SO OBTAINED (4) NEUTRALISING SAID SULPHONIC ACID AND WORKING UP THE REQUIRED PRODUCT. 